The present invention relates broadly to an imagery compression system, and in particular to a simultaneous amplitude sequency system.
A wide variety of data compression systems are known to the art. Usually, data compression is effective only in cases where a redundant digital code is employed, or where the data is redundant in nature by its very content. As an example of the latter situation is in digital video, facsimile or other graphic systems wherein data bits relate to graphical presentations of some sort. Such systems may include weather map transceivers, picture phone, medical display, navigational displays and digital sonar and radar presentation systems, including scan converters. One well known form of data compression system is a coarse/fine system wherein during periods in which the video intensity is changing very slowly, only fine changes are transmitted, and where it is changing rapidly, only coarse changes are transmitted. However, such systems are rather complex and require considerable hardware or significant utilization of a special purpose computer to be mechanized. On the other hand, a form of data compression known as delta modulation, which simply changes the video level by one gray level at a time from one picture resolution element to the next, has been utilized. However, areas of high spatial frequency content (rapid changes in video level) are distorted because of the limited system slow rate.
In any data compression system, it is essential that the additional hardware which is required to compress the data must be much less bulky and costly than the hardware that it allows to be removed in order for the overall system cost and complexity to be reduced by means of data compression. Further, the data compression should not sacrifice necessary performance or video quality.